The central and fundamental proposition of socialism is not any scheme for reconstructing society, on a cut-and-dried programme, nor again is it any particular mathematical formula showing to what extent the laborer is robbed by the present system of the fruits of his labor; it is precisely this Historical Materialism, which Labriola has so admirably explained in the present work.Some idea of the place accorded to this book by European socialists may be gathered from the preface to the French edition by G. Sorel, one of the most prominent socialists of France.